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Popping on Decel / Noisy engine?

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Got the 2005 DRZ400 i picked up running- needed a carb scrub and some tuning done. Changed the oil, lubed the chain, and did general maintenance since it hasn't been loved since last September. 

 

Took it out for an hour last night- Pulls great and is a blast to ride, but two issues have me worried. 

 

1) the common complaint of "popping on deceleration". i'm not sure if the jets are stock- stupid me didn't look at the numbers while I had them out. It has an aftermarket Yoshimura exhaust (Im thinking it's an RS2 Comp series), and 3x3 already done. Thankfully, PO installed a quick-adjust F/A screw, which i've been tweaking around. When I first had it running, it would pop on throttle, and often stall. I took it out today and as I was rolling from a cold engine, it stuttered and shot pretty loudly. I've richened that up, which helped, but didn't eliminate ALL of the issues.

 

At WOT, it seems to hold fine, and i'm not exactly getting any indicators for lean/rich conditions (bogging or RPMs hanging), except for on decel, you can hear it popping as the RPMs fall. Sometimes if you blip or drop the throttle, there will be a slight afterpop / change in note.

 

I'm not entirely sure which aspect to address in the carb. My KLR did this when i first got it, too, and I had to switch out the needle to a more aggressive taper with adjustable levels, and size the main jet up. I'm no carb whisperer, however, so i'm wondering what's falling short and causing the issues.

 

One more thing to mention: when i opened it up to clean, I noticed two things were missing that were on the parts diagram for the carb (hopefully i found the right diagram!) - #18 (Jacket thingy which goes on the float needle w/ O-ring????) and #62 (Tiny o-ring in the "dead zone"?. The bike seems to run fine, but i'm wondering if these could contribute to it acting wonky:

 

2014-05-24%25252016_19_30-Image.gif%2525

 

Here's a pic for ref:

 

2014-05-24%25252016_05_19-Max%252520Mong

 

2) The top-end is super noisy at idle. I'm used to some cam chain noise on my 2000 Super Sherpa, so part of me wants to believe it's just normal. It's sort of a whine/ticking/thunking. It has a 434 Big Bore kit on it, but it's rather noticeable even from a distance- Normal, or worrysome? It doesn't get louder as i rev, but i might not be hearing it from tire howl / wind noise. I'd assume if it were a rod, timing issue, or other Uh Oh Engine Explode issue, it'd make itself very apparently, very quickly. I'll try to shoot a video of the noise once I have my equipment ready to do so for a better demonstration.

 

Thanks for any input!

 

 

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1.) Have you checked the cam chain adjustment?  First place I would look :thumbsup:
2.) Start over with checking jets and replace what is missing. You may have to re-jet or set your clip on the needle up or down.

Edited by DRZ-Nut

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Decel pop-lean condition on the pilot circuit, it may not be a blocked pilot jet or even incorrect FA screw...check no dirt is lodged in the air feed for the circuits. Another thing is the exhaust... Make sure it's tight and there is no chance of an air leak.

Aftermarket pipes usually need jetting changes, some minor some major. Chop tests and plug readings are a good way to go!!

Engine noise-timing chain rattle could suggest it's time for another chain. If it has a decomp on the exhaust cam that'll make a racket at idle. Check your clearances on the valves too.

Those 'missing parts' are vital-make sure you replace them!! And any other gaskets/o-rings.... Leaks of any kind spell havoc on the carb performance.

Also, the FA screw-did you get the o-ring/spring/washer combination correct and is the o-ring new?

Remember that under decel with the throttle side shut off the vaccum created is tremendous, any possible way for air to enter the cylinder is going to have a negative effect on things.....

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Popping on deceleration (to a degree) is normal with aftermarket (straight-thru) exhausts.  Start with adjusting the idle mixture screw (richer) a 1/4 T at a time.  Remember its a compromise… so don't set it too rich and have issues like dipping RPMs at idle and bogging under WOT.

 

As far as the top-end noise, yeah DRZs are noisy.  First, start by checking the MCCT (look in the DRZ400 FAQ section on how to set it).  Second, check/adjust the valve clearances, but generally a noisy engine means large valve clearances (which is "okay").  Third, while you're checking the valves inspect the auto-decomp mechanism as those can cause noise too.  However more importantly check that its all there and functioning correctly (search forum, example).

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Thanks for the responses, all. Going to condense everything so i can address each with further data:

 

 

On the engine noise....

Engine noise-timing chain rattle could suggest it's time for another chain. If it has a decomp on the exhaust cam that'll make a racket at idle. Check your clearances on the valves too.

 

As far as the top-end noise, yeah DRZs are noisy.  First, start by checking the MCCT (look in the DRZ400 FAQ section on how to set it).  Second, check/adjust the valve clearances, but generally a noisy engine means large valve clearances (which is "okay").  Third, while you're checking the valves inspect the auto-decomp mechanism as those can cause noise too.  However more importantly check that its all there and functioning correctly (search forum, example).

 

1.) Have you checked the cam chain adjustment?  First place I would look :thumbsup:

 

 

Stevo- New chain at 5k? seems rather soon to be replacing the cam chain, unless PO just absolutely thrashed it...

 

I'll check valves however and screw around with the MCCT and report back. Maybe i'm being neurotic and just not used to the way this engine sounds. I need to do less worrying and more riding.

 

 

 

On carb reassembly....

Also, the FA screw-did you get the o-ring/spring/washer combination correct and is the o-ring new?

 

Yep, or i'm assuming I did.  In order of what I dropped in the hole first:  O-ring->washer->spring->screw ---right?

 

 

On decel pop....

 

2.) Start over with checking jets and replace what is missing. You may have to re-jet or set your clip on the needle up or down.

 

 

Decel pop-lean condition on the pilot circuit, it may not be a blocked pilot jet or even incorrect FA screw...check no dirt is lodged in the air feed for the circuits. Another thing is the exhaust... Make sure it's tight and there is no chance of an air leak.
Aftermarket pipes usually need jetting changes, some minor some major. Chop tests and plug readings are a good way to go!!

Remember that under decel with the throttle side shut off the vaccum created is tremendous, any possible way for air to enter the cylinder is going to have a negative effect on things.....

 

Popping on deceleration (to a degree) is normal with aftermarket (straight-thru) exhausts.  Start with adjusting the idle mixture screw (richer) a 1/4 T at a time.  Remember its a compromise… so don't set it too rich and have issues like dipping RPMs at idle and bogging under WOT.

 

DRZ: Does the stock needle have adjustment notches? I'll admit I wasn't paying attention when I was cleaning it. A lot of people say to buy a Dynojet kit and some jets. Peered over this article: http://www.4strokes.com/tech/suzuki/drz400su.asp, which said to get a dynojet stage one kit, and go to a 25 pilot, or adjust F/A out aggressively- i'm just curious what would be the best for this Yoshimura pipe

 

Stevo: Gave it a pretty thorough cleaning / blow-out. Haven't checked for any exhaust leaks- I'll do that tomorrow (does anyone have a list of torque values for the DRZ handy?). I hear ya on the decel vacuum, hence why i'm trying to right it- i'd hate to grenade the engine due to hyperlean conditions thanks to leaking.

 

BMW: I've dialed it out a few times, quarter turns like you said- still no bogging, though sometimes it seems like it will load up on fuel then let out one low GLUBPOP at lower RPMs. WOT is fine, or seems it- If you slam back, it screams away without hesitation- definitely a lot more throttle response than the KLR or Sherpa also in my hangar. Wonder if i should keep adjusting out...

 

 

 

On missing parts....

Those 'missing parts' are vital-make sure you replace them!! And any other gaskets/o-rings.... Leaks of any kind spell havoc on the carb performance.
Also, the FA screw-did you get the o-ring/spring/washer combination correct and is the o-ring new?

 

I may be overlooking something, but is #18 in the diagram, the brass seat that the float needle fits into / is inset into the carb? It was still in there when i cleaned it (i didn't remove it... honestly didn't know it came out, if it does!), but when I looked over the diagram, I was unsure if it was something external that went over the float needle for...whatever reason... I first started looking to see if something fell out during disassembly, but nope- I had it all on my workbench, and didn't miss a single piece- but this isn't to say that the PO didn't miss it!

 

If that's the case, all i'd need is that stupid little "dead-zone" o-ring-- what does is DO anyways? There was a groove in the diaphragm cover, but it didn't seem to go anywhere. On this carb, PO capped off the hose coming from the top... This bike gets more and more bizarre each day I look at it.

 

If i DO need to replace it... http://www.ronayers.com/VALVE-ASSYNEED-P3053176.aspx   Crap that's kinda expensive!

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Pulled the plug to check it out. It's not super frosty, but it's rather clean with black bands near the base of the thread-- dont know how old this plug is, but ive maybe done 100 miles on the bike since picking it up, which i hope is enough to get a good plug reading.

 

Pics are attached- thoughts?

 

*EDIT* Clatter was MCCT:cheers: 

DSC_0510.JPG

DSC_0509.JPG

DSC_0507.JPG

Edited by Cynictis

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Pulled the plug to check it out. It's not super frosty, but it's rather clean with black bands near the base of the thread-- dont know how old this plug is, but ive maybe done 100 miles on the bike since picking it up, which i hope is enough to get a good plug reading.

Pics are attached- thoughts?

*EDIT* Clatter was MCCT - :cheers:

If you do figure out what is causing your ruckus on decel can you post it? I would like to know because I am having all the exact same issues/symptoms as you. Thanks.

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If you do figure out what is causing your ruckus on decel can you post it? I would like to know because I am having all the exact same issues/symptoms as you. Thanks.

 

Not yet. I'm assuming it's poor jetting introducing a lean condition somewhere. i'll update when i've found it.

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 all i'd need is that stupid little "dead-zone" o-ring-- what does is DO anyways? There was a groove in the diaphragm cover, but it didn't seem to go anywhere.

That little o-ring is necessary, it seals the vacuum circuit for the slide and without it it will leak and the slide will not raise properly as the butterfly is opened.

 

As far as the deceleration pop try the clip in # 4  if you can't dial it out with the fuel screw.

On mine I tried 25 pilot,clip #3 and fooled with the screw and never got any improvement, went back to the 22.5 and clip #4 and it pretty much eliminated the popping.  

Edited by Kioti
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That little o-ring is necessary, it seals the vacuum circuit for the slide and without it it will leak and the slide will not raise properly as the butterfly is opened.

 

As far as the deceleration pop try the clip in # 4  if you can't dial it out with the fuel screw.

On mine I tried 25 pilot and fooled with the screw and never got any improvement, went back to the 22.5 and clip #4 and it pretty much eliminated the popping.  

 

Just went and picked one up. Not an exact fit, but hopefully it will work...

 

I'll try fooling with the clip position, considering i have to open up the diaphragm cover anyways to install the O-ring. I've backed the F/A screw out pretty aggressively, and while it helped, it didn't eliminate. What's your main jet / what elevation are you at? i'm between 800-3000ft ASL here depending on which road i take!

 

 
:thumbsup:  Appreciate it.
Edited by Cynictis

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Just went and picked one up. Not an exact fit, but hopefully it will work...

 

I'll try fooling with the clip position, considering i have to open up the diaphragm cover anyways to install the O-ring. I've backed the F/A screw out pretty aggressively, and while it helped, it didn't eliminate. What's your main jet / what elevation are you at? i'm between 800-3000ft ASL here depending on which road i take!

 

 
:thumbsup:  Appreciate it.

 

900 ft.always as I'm in Kansas lol.

'09 model air box modded but not the full 3x3, GSXR 600/750 muffler.

JD blue needle clip 4th from top

22.5 pilot

150 main

extended fuel screw 2.5 turn out.

Edited by Kioti

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900 ft.always as I'm in Kansas lol.

'09 model air box modded but not the full 3x3, GSXR 600/750 muffler.

JD blue needle clip 4th from top

22.5 pilot

150 main

extended fuel screw 2.5 turn out.

 

Pulled the carb apart just now. Needle clip is at 4th position - 22.5 stock pilot, and 142.5 main jet... wonder if I should go up one on the main?

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and 142.5 main jet... wonder if I should go up one on the main?

142.5 is stock,with the 3x3 and yosh exhaust I'd bump it up to 150-155.

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Pulled the plug to check it out. It's not super frosty, but it's rather clean with black bands near the base of the thread-- dont know how old this plug is, but ive maybe done 100 miles on the bike since picking it up, which i hope is enough to get a good plug reading.

 

Pics are attached- thoughts?

 

*EDIT* Clatter was MCCT:cheers:

Your plug looks fine, a lot better than some Ive seen on here, that's the way it should look. Most hear are way rich and full of carbon

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